The storm will douse Baja California with 3 to 6 inches of rain, with some spots getting up to 10 inches, the National Hurricane Center
said.

As it moves northeast Rosa will also dump 2 to 4 inches of rain on much of Arizona, with up to 6 inches in the Arizona mountains.

Historically, it's unusual for the US Southwest to get pummeled by a hurricane or tropical storm. But "these events have begun to increase in recent years," CNN meteorologist Gene Norman said.

Research indicates that global warming contributes to tropical storms getting "more intense, bigger and longer-lasting, thereby increasing their potential for damage," said Kevin Trenberth
, senior scientist at the National Center for Atmospheric Research.

While there might not be a direct link between global warming and the recent increase of severe storms in the US Southwest, "it is possible that this could be a side effect of climate change," Norman said.

"Warmer oceans are allowing eastern Pacific storms to reach higher latitudes," he said. "This was not the case earlier. It was quite rare for an eastern Pacific storm to even reach Baja California, and this now becoming more common."